Human beings are social creatures. Feeling like we’re part of a community helps us thrive. But we sometimes have a hard time making and keeping the relationships that sustain us. Many Americans report feeling lonely for long periods of time. Connections with others are important for your health.

Social isolation and loneliness can both cause problems. “Isolation is about whether other people are physically there or not. Being lonely is about not feeling connected to others. You can feel lonely in a room full of people,” explains Dr. Steve Cole, an NIH-funded researcher at the University of California, Los Angeles, who studies loneliness.

Loneliness not only feels bad, it may also be harmful to your health. People who feel lonely are at higher risk of many diseases. These include heart disease, high blood pressure, and Alzheimer’s disease. Loneliness may also increase the risk of death for older adults.

Some of the increased risk of disease may come from changes in behavior. People who feel isolated may not have friends or family encouraging them to eat right, exercise, or see a doctor. New research suggests that loneliness can also directly harm our health.

“Lonely people have differences in their biology that make them more vulnerable to disease,” Cole explains. He and colleagues have studied how loneliness affects the immune system, your body’s disease fighting system. They found that loneliness may alter the tendency of cells in the immune system to promote inflammationHeat, swelling, and redness caused by the body’s protective response to injury or infection.. Inflammation is necessary to help our bodies heal from injury. But when it goes on too long, it may raise the risk of chronic diseases.

People who feel lonely may also have weakened immune cells that have trouble fighting off viruses. “So that leaves lonely people more vulnerable to a variety of infectious diseases,” Cole adds.

People often associate loneliness with getting older. But you can feel lonely at any age. A recent survey found that young Americans are more likely to feel lonely than older adults. Some research suggests that social media tools and resources are preventing younger people from connecting in real life, Cole says. However, more studies are needed to know whether this is true.

It can be hard for people to talk about loneliness, Cole explains. They may feel like something is wrong with them, even though feeling lonely happens to almost everyone at some point.

NIH-funded researchers are looking into ways to help people break the cycle of loneliness. Studies have shown that feelings of loneliness can be reduced by helping others, Cole says. Caregiving and volunteering to help others may therefore help people to feel less lonely.

Having a sense of purpose in life may be another way to fight the effects of loneliness. Research has found that having a strong sense of mission in life is linked to healthier immune cells. “And when you start to pursue a goal that’s important to you, you almost always have to cooperate with others to do that,” Cole says. “That helps bring people together.”